The ink jet recording system is a printing system in which ink droplets are discharged through minute jet nozzles of a recording head according to image data, and allowed to adhere to a recording medium, thereby making a print By the recent innovative progress of the ink jet recording technology, ink jet recorded matter of high gloss, high image quality and high keeping quality has come to be obtained, but has not reached a level comparable to silver salt photographs under the present circumstances. Recently, in order to achieve high keeping quality comparable to silver salt photographs, pigment inks excellent in water resistance, light resistance and the like compared to dye inks have come to be used as inks for ink jet recording.
As the technical problem of ink jet recording using the pigment inks, there has been the problem that so-called uneven gloss occurs, particularly when highly lustrous media are used as the recording media. The uneven gloss is a phenomenon in which the difference in gloss occurs between a background area (a non-print area on which the gloss of the medium itself appears) and a print area, between a plurality of colors even in the print area, or between light and shade even in the same color Further, recorded matter on which an image is formed by the pigment ink (pigment ink recorded matter) also has the problem of poor sharpness in visual observation, compared to silver salt photographs. Furthermore, the image of the pigment ink recorded matter is formed by pigment particles adhered to a surface layer of the recorded matter, so that the image is sometimes separated or stained when rubbed against another object. A problem is therefore encountered with regard to abrasion resistance in many cases.
As a process for solving such problems of the pigment ink recorded matter, it is conceivable to form a resin layer such as a transparent film or the like on the surface of the image formed. As for this resin layer formation process, a large number of methods have been proposed mainly for dye ink recorded matter, and a method of melt laminating polyethylene or polypropylene, a method of laminating a polyethylene film or a polypropylene film by bonding, and the like are well known. However, in these laminating methods the resin layer must be thickened to some extent in order to impart thereto such adhesiveness or adhesion that does not develop a so-called pinhole and that does not cause separation from the surface of the image under ordinary use conditions. However, the resin layer having such a thickness has the problems of deteriorating image quality, causing uncomfortable dazzling, developing curl, and the like.
As an improved technique of the above-mentioned laminating methods, JP-A-60-23096 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-60-189486 and JP-A-61-230973 disclose a method of using a protective layer-transferring film comprising a film and a protective layer (resin layer) relesably provided thereon, and heat transferring the protective layer onto the surface of an image of recorded matter, thereby easily providing the protective layer on the image. Further, JP-A-8-174989 discloses a method of providing on recorded matter a transfer overcoat layer melt transferred via a heat-resistant film and mainly composed of a thermoplastic resin. According to the heat transfer methods using such protective layer (resin layer)-transferring films, it becomes possible to form thin resin layers, compared to the above-mentioned laminating methods. Accordingly, the uneven gloss of the pigment ink recorded matter, and poor image sharpness and abrasion resistance can be solved without bringing about deteriorated image quality.
The conventional protective layer-transferring film for the heat transfer method on which the transferable protective layer is relesably formed on the heat-resistant film has the problem that transfer easiness of the protective layer to the recorded matter is so pursued that adhesion between the heat-resistant film and the transferable protective layer becomes insufficient, which causes separation or dropout of the transferable protective layer from the heat-resistant film in slitting or in a heat transfer operation. On the other hand, the transferable protective layer excellent in adhesion to the heat-resistant film poses the problem of poor gloss-imparting effect to the recorded matter, and no protective layer-transferring film excellent in both the transfer easiness and gloss-imparting effect has been provided yet. Further, the conventional protective layer-transferring film also has the problem that so-called blocking occurs in which a sticky surface of the transferable protective layer comes into contact with and sticks to a back side of the heat-resistant film, and the transferable protective layer is transferred to the back side in an extreme case, when the protective layer-transferring film is wound up and stored in the roll form, because the transferable protective layer deteriorates with time to make the surface thereof sticky in some cases.